[Elecraft] dynamic range question was [FT817] ELECRAFT

Fri Dec 30 08:47:58 EST 2011

Don:

Dynamic range is the ratio or the largest signal to the smallest signal 
that the receiver can properly handle.

The low end of dynamic range is smallest signal that the device can 
detect, and in analog gear like an amplifier or mixer is usually 
determined by the internal noise generated by the device. This is the 
"noise floor." It is the strength of the weakest signal just barely 
discernible in the noise. Typically, the noise floor occurs where the 
rms value of the signal equals the standard deviation of the noise.

The high end of the dynamic range is the largest signal for which output 
of device remains undistorted. A signal above the top end of the dynamic 
range will produce a distorted output, and will change the properties of 
the device such as reducing its gain for all signals.

In practice this causes problems if you are trying to listen to a 
relatively weak signal, and a few kHz away (outside your roofing filter 
window, but inside the band) "Doub-You Five Texas Kilowatt" fires up the 
big rig. Suddenly, your weak signal vanishes, because the front end of 
your rig is "desensed" by the nearby large signal. Since the interfering 
signal is outside your roofing filter range, you do not actually hear 
the interfering signal itself, but your reception of the desired signal 
is disrupted by its effect.

Improve the dynamic range of your receiver by 30 dB, and now the 
interfering station needs a Texas megawatt instead of a Texas kilowatt 
to cause you the same level of disruption as before.

73 & HNY,

Steve
AA4AK

On 12/30/2011 7:51 AM, goldtr8 at charter.net wrote:
> Ok I admit I do not clearly understand this 30dB better dynamic range.
>
> Can someone put it into terms what this really means on the RX side of
> things, when you would be in real world operating conditions.  It does
> not have to be about these specific radios listed in the post below, but
> what does this dynamic range really mean when comparing specfications.
>
> Thanks and Happy New Year.
>
> Don
>
> ~73
> Don
> KD8NNU
>
>
> On Thu, Dec 29, 2011 at 9:33 PM, Wayne Burdick wrote:
>
>> Matt,
>>
>> The KX3 will have about 30 dB better dynamic range than the IC-7000,
>> even without the roofing filter.
>>
>> I'm not knocking the 7000 -- it's a versatile little rig. It's just a
>> question of how much RX performance you want. Of course the KX3's
>> ergonomics are completely different, too.
>>
>> 73,
>> Wayne
>> N6KR
>>
>> On Dec 29, 2011, at 5:43 PM, Matt Maguire wrote:
>>
>>> Hi Johnny,
>>>
>>> I thought about an FT817, but my reasoning was similar to the points
>>> you listed. In addition, a friend of mine lent me an FT817 to play
>>> with, and to do the least little thing you need to go menu diving.
>>> On the Elecraft gear, most of these common functions seem to be
>>> readily accessible from the front controls.
>>>
>>> As you point out, a used K2 could be a very good deal. The main
>>> problem with a used K2, though, is that you miss out on all the fun
>>> of building it yourself :-)  I must admit, earlier in the year I was
>>> thinking about a K2, but was a bit worried about the size for a
>>> portable setup. But then of course the KX3 was announced, which fit
>>> my requirements perfectly.
>>>
>>> I have ordered a KX3 without a roofing filter, so it will be
>>> interesting to see how well it performs with just the DSP filtering.
>>> I do love the flexibility of the DSP filtering on my IC7000.
>>> However, the nice thing about the KX3 is that I have the option to
>>> add a roofing filter later if I find it is needed, whereas in the
>>> IC7000, I don't think adding/narrowing IF filtering before the DSP
>>> is really feasible.
>>>
>>> 73 Matt VK2ACL.
>>>
>>>
>>> On 30/12/2011, at 11:54 AM, Johnny Siu wrote:
>>>
>>>> I once used FT817ND for portable operation but I eventually gave  it
>>>> up and replaced it by a K2. My reasons are:
>>>> ...
>>>> 1.  I was disappointed by the RX performance of FT817 and K2 is far
>>>> better.  FT817 is hot enough to receive everything but I cannot
>>>> select the station I wanted - very poor selectivity indeed;
>>>> 2.  Current drain of K2 is as low as 180ma;
>>>> 3.  Built-in ATU of K2 (swr 10:1) is convenivent;
>>>> 4.  Built-in speech processor of K2 gives much more talk power;
>>>> 5.  K2 can deliver more power at 10-15W;
>>>> 6.  The V/U operation of FT817 can be covered by H/T
>>>> 7.  A full loaded FT817 with filters, OBP processor etc is not that
>>>> cheap
>>>>
>>>> Most of the above rationale also applies to the decision between
>>>> KX3 Vs FT817 though it is not quite an apple to apple comparison.
>>>> Having said that, I still consider FT817 is very value for money
>>>> because its price in VR2 is less than US$600.
>>>>
>>>> With the coming of KX3, I notice many good deals for used K2.  If
>>>> you do not too keen on v/u, used K2 could be a good buy.
>>>>
>>>> TNX&  73,
>>>>
>>>>
>>>> Johnny VR2XMC
>>>>
>>>> 從︰ egsise<egsise at yahoo.com>
>>>> 收件人︰ FT817 at yahoogroups.com
>>>> 傳送日期︰ 2011年12月30日 (週五) 7:40 AM
>>>> 主題︰ [FT817] Re: ELECRAFT
>>>>
>>>>
>>>>
>>>> Ok ok the KX3 looks good on paper, relax it's not an iphone you
>>>> need to defend.
>>>> To be honest it's not the price that matters so much, it's just not
>>>> tested yet.
>>>> So I highly doubt that the battery drain is lower than
>>>> FT-817's(actually FT-817 battery drain is not that bad).
>>>> I doubt that the digital modes are not as easy to operate portable
>>>> as FT-817 paired with touchscreen smartphone.
>>>> If the firmware has bugs then it's nice to do the upgrades of
>>>> course..
>>>>
>>>> I read somewhere that it all starts from A as antenna.
>>>> O for operator, and last is R as rig.
>>>> I guess from those three the rig affects least to how many contacts
>>>> you make.
>>>>
>>>> Jani OH9FZU
>>>>
>>>> --- In FT817 at yahoogroups.com, "dyarnes1"<w7aqk at ...>  wrote:
>>>>> Hi All,
>>>>>
>>>>> The KX3 won't appeal to everyone, particularly those who highly
>>>>> value the 817's ability to cover 2 and 440. However, even a
>>>>> "stock" KX3 will run circles around an 817 in performance and
>>>>> features. You get true QSK, a better display, firmware upgradeable
>>>>> (which Elecraft does better than anyone), Better DSP, PSK31 and
>>>>> RTTY w/o a computer, much lower battery drain, 8 band equalizer
>>>>> for both receive and transmit, etc. All this in a package that is
>>>>> actually smaller and lighter than the 817, and the KX3 even runs a
>>>>> little more power.
>>>>>
>>>>> The actual price differential is more like $250 comparing "stock
>>>>> model to stock model", and including the microphone. That's not
>>>>> all that much for the additional performance capability in my
>>>>> view. Admittedly I priced the "kit" version, but putting these
>>>>> together is very, very simple. It's just "assembling", not
>>>>> building. What drives the price up is all the extra goodies that
>>>>> you can't even get for the 817, mainly the ATU and the narrow
>>>>> roofing filters. The ATU option is, in my view, a "must" have
>>>>> considering how well Elecraft ATU's perform.
>>>>>
>>>>> There seems to be enough "apples and oranges" differential between
>>>>> the two radios to make it difficult for a lot of folks to see the
>>>>> benefit in switching. However, I don't think "value" is really a
>>>>> valid concern. It's more a matter of just what do you need to be
>>>>> happy? Isn't it great to have a choice!
>>>>>
>>>>> Dave W7AQK
>>>>>
>>>>>
>>>>>
>>>>> --- In FT817 at yahoogroups.com, "wildergeek"<kb8ybs@>  wrote:
>>>>>> $1,400 for a KX3 equipped the way I'd want it. Think I'll stick
>>>>>> with my upgraded 817 for a while longer...
>>>>>>
>>>>>> Greg
>>>>>> KB8YBS
>>>>>>
>>>>>> --- In FT817 at yahoogroups.com, "Richard"<f6driver@>  wrote:
>>>>>>> I'm very interested in the KX-3 and am on their list.
>>>>>>> I think the receiver on my 817 really does need some serious
>>>>>>> help, like a narrow IF filter and W4RT DSP mod,
>>>>>>> and.............the point is why sink another $500 into a 10
>>>>>>> year old radio instead selling it and use the proceeds towards a
>>>>>>> KX-3 state of the art SDR QRP portable.
>>>>>>> Either way I play it, it's going to cost, so why not end up with
>>>>>>> the newer technology?
>>>>>>> I'm ready to get flamed for saying this here, but still would
>>>>>>> like to hear any arguments that make sense.
>>>>>>> Richard
>>>>>>> KE4UN
>>>>>>>
>>>>
>>>>
>>>>
>>>> [Non-text portions of this message have been removed]
>>>>
>>>>
>>>>
>>>> ------------------------------------
>>>>
>>>> and for a great FAQ ( Frequently Asked Questions ) see
>>>> http://groups.yahoo.com/group/FT817/database
>>>> Some really good technical info at:
>>>> http://www.ussc.com/~turner/ft817pg.shtml
>>>> Please note that your messages and files sent to this group may
>>>> appear anywhere on the Internet or in print without notice or
>>>> compensation.
>>>>
>>>> Yahoo! Groups Links
>>>>
>>>> <*>  To visit your group on the web, go to:
>>>>    http://groups.yahoo.com/group/FT817/
>>>>
>>>> <*>  Your email settings:
>>>>    Individual Email | Traditional
>>>>
>>>> <*>  To change settings online go to:
>>>>    http://groups.yahoo.com/group/FT817/join
>>>>    (Yahoo! ID required)
>>>>
>>>> <*>  To change settings via email:
>>>>    FT817-digest at yahoogroups.com
>>>>    FT817-fullfeatured at yahoogroups.com
>>>>
>>>> <*>  To unsubscribe from this group, send an email to:
>>>>    FT817-unsubscribe at yahoogroups.com
>>>>
>>>> <*>  Your use of Yahoo! Groups is subject to:
>>>>    http://docs.yahoo.com/info/terms/
>>>>
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:Elecraft at mailman.qth.net
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Elecraft at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html